杂质铝对磷酸酯混合萃取剂从铵盐浸出液中萃取稀土的影响

Effect of Aluminum Impurity on Extraction of Rare Earth From Ammonium Salt Leaching Solution with Phosphate Ester Mixed Extractant

风化壳淋积型稀土矿是我国重要的战略性资源,使用原地浸出开采工艺得到的稀土浸出液中铝含量较高,是主要的杂质离子。为了从该浸出液中一步法分离富集稀土,探讨了一种磷酸酯混合——萃取剂P0261(2-乙基己基磷酸酯,单酯和二酯1GA6FA1混合)在NH4Cl、(NH4)2SO4、NH4NO3三种模拟浸出液中对稀土La3+、Nd3+的萃取行为,并分析杂质铝离子对稀土萃取行为的影响。试验结果表明:在三种铵盐溶液中,萃取剂均能够有效萃取分离稀土离子La3+、Nd3+;加入Al3+后,稀土萃取率E会随Al3+浓度增大而减小。但当Al3+浓度在300 mg·dm-3以内时,E降幅缓慢,最大下降值为14.68%。通过分析负载有机相,Al3+比RE3+更易与P=O形成配位键,且铵根离子浓度变化会影响P=O→RE配位键的形成,从而影响萃取行为。因此,将浸出液中的杂质铝离子浓度控制在300 mg·dm-3以内,则可以使用萃取剂P0261一步法萃取分离稀土。

The weathered shell leaching type rare earth ore is an important strategic resource in China.The rare earth leaching solution obtained by in situ leaching process has high content of Al3+and is the main impurity ion.In order to separation rare earth ions from leaching solution by one-step way,the extraction behavior of a phosphate ester extractant,P0261(2-ethylhexyl phosphate,1GA6FA1 mixture of mono ester and diester),was investigated for rare earth ions La3+、Nd3+in three simulated leaching solutions of NH4Cl,(NH4)2SO4 and NH4NO3,and the effect of impurity Al3+on the extraction behavior of rare earth was also analyzed.The results show that the extractant P0261 has good extraction affinity towards rare earth ions La3+and Nd3+in the three kinds of ammonium salts solution.With the addition of Al3+,the extraction rate E of rare earth ions decreases with the increase of Al3+concentration.E declines slowly when C(Al3+)at 0~300 mg·dm-3,while the maximum reduction of E is 14.68%.By analyzed the load organic phase,Al3+was easier to coordination bonds with P=O than RE3+,and the change of NH4+concentration has novel effect on the formation of P=O→RE coordination bonds,which was one of the reasons caused the change of rare earth extraction behavior.From experimental results,control the C(Al3+)below 300 mg·dm-3 in in-situ leaching solution,the effect of impurity ion on selective extraction and separation rare earths by one-step way using extractant P0261 is accepted.